GB982686A - Superconductive electrical devices - Google Patents

Abstract

982,686. Transformers. INTERNATIONAL RESEARCH & DEVELOPMENT CORPORATION. June 6, 1961, No. 20357/61. Heading H1T. In a superconductive transformer the primary and secondary windings comprise a plurality of coil layers, the layers of one winding being interleaved with the layers of the other winding to mimimize the magnetic fields linking the coil conductors there being a critical value of flux beyond which the superconductive state is destroyed. The windings are of wire or foil and may be in concentric cylindrical helical coil layers as Fig. 3 or interleaved disc coils (Fig. 15, not shown). The primary and secondary conductors may be of the same gauge and have the same number of layers, the coils of one winding being connected in series parallel and of the other in series (Fig. 4, not shown). The coils may be wound on phenolic plastic former and the conductors may be insulated with " Teflon " (Registered Trade Mark) and may be of tin, niobium or lead. The windings are enclosed in a heat insulation jacket connected to a refrigeration system and the core is outside the jacket (Fig. 7, not shown). As shown sectionally in Fig. 10, the jacket is in the form of a toroidal shaped double Dewar vessel comprising an outer vessel having an outer glass wall 26 separated by a vacuum space 27 from an inner glass wall 28 and an inner vessel having inner and outer glass walls 29, 31 separated by a vacuum space 30. The middle volume between walls 28, 29 is filled with liquid nitrogen 32 and the volume between the wall 31 and the windings is filled with liquid helium 33, and the vacuum space walls may be silvered. A method of forming the Dewar vessels around the preformed coils is briefly described. The leads to the transformer winding, which may be of copper, nickel or aluminium, pass through a ducting into the Dewar vessel jacket and in order to reduce the power required for the refrigeration of the windings the leads may be subjected to several stages of refrigeration before entering the jacket (Fig. 13, not shown). The application to single and three phase transformers is suggested and some design details for a 10MVA transformer are given.